What is the best glue for sticking down a mini cell foam piece to my sea kayak seat. I have tried evo stick contact adhesive but am not overly impressed with it. It always ends up coming up on the edges after a few outings. I used to have a similar piece on my Tiderace boat but that never came off at all.Trying to do a really tidy job and prmenant fix?

Contact adhesive works best if you coat the surfaces first, leave them to dry hard (24hrs +), then recoat following the instructions. This is particularly useful when glueing to polythene but helps with grp as well.

When your foam comes unstuck, does the glue separate from the foam or the seat?

It might be the surface is a bit salty, dusty or greasy. When I glued my foam seat in (with contact adhesive) I cleaned with acetone, lightly sanded, then cleaned with acetone again (to remove the dust), then masked the area and did what Chris suggests, coated with adhesive and left to dry etc. Worked fine. That was in a composite boat mind.

Depending on the glue - consider using two layers - let the first one go tacky before applying the second layer. It's also a good idea to roughen the seat if possible.

It might be worth using something like Black Witch around the edges, or even something like Gaffer tape to keep the surfaces together at the edge. Also consider trimming the foam so that it tapers at the edge (so there isn't a "step") and also avoid sharp corners; try to make them rounded, or at least do a 45 degree snip.

If it is a plastic (polyethelene or similar) it may be worth flame treating before glueing to increase the surface energy. If you decide to flame the surface it is a very quick treatment with an oxidising flame, it should not be enough to make the object hot.
Ken

Well, Ceegee's advice would mirror what I did in fixing foam to a f/glass seat - which is essentially the same as yours. It went on the sides of the seat, so is subject to a sheering force every time one gets in or out, and has been fine since I did the job 2 years ago.